Quantitative Skills > Teaching Resources > Activities > Modeling the interior of the Earth using Seismic Waves

Modeling the interior of the Earth using Seismic Waves

Eric M. D. Baer, Dusty Wilson, Tina Ostrander

Highline Community College, Des Moines, Washington
Author Profile


This is an inquiry-based student exercise designed to explore how we use seismic waves to understand the structure of the Earth's interior. Students test several models of the interior of the Earth beginning with a simple homogeneous Earth and moving toward more complex multi-layered Earth models. First, students test the viability of a homogeneous (one-layer) Earth using observed P-wave arrival times throughout the globe. Subsequently, the practicality of a two-layer model is explored as students graphically determine ray paths and travel times and perform simple calculations of Snell's law. Finally, students are asked use a publicly available Java program to calculate wave travel times through a model of Earth that they create (with as many or as few layers as they see fit). The ultimate goal involves student generation of a model that reproduces actual measured seismic travel times as closely as possible.

Learning Goals

Northridge Earthquake image At the end of this exercise, students should be able to: At the end of this exercise students may be able to:

Context for Use

Interior of the Earth

I use this lab in both an intro-physical geology class and a non-majors seismology class. The students will have to know about seismic waves beforehand, but there is very little other assumed knowledge. The whole project can take 3-4 hours. The first module, which looks at travel times through a homogenous earth, is useful if you want just a 1 hour or less activity to begin the a discussion of how we use seismic waves to tell what the interior of the Earth is like.

Teaching Notes and Tips

For the whole activity I generally use 2 2-hour lab periods. However, because the assignment is open ended, students can take significantly longer. The instructor will need to decide how close they want the student results to be to the actual measured velocities or give them a time limit.

Students will need paper, pencil, protractor, ruler, and a calculator with trigonometric functions. They will also need an internet-connected computer with the current version of Java installed for the third part of this activity.

One common problem with this lab is that the Java program won't run. This is because you don't have the most current version of Java. The applet for module 3 does not run in Java 1.4, but does in 1.5

Teaching Materials

The output of the JAVA program for a 2 layered Earth
There are several documents you will need for this lab: Curious how this project came be? Need some diagrams to help explain the concepts? Try this powerpoint presentation (PowerPoint 906kB Feb9 06) and see if it helps.
Finally, you will need the location of the JAVA applet, which is at http://www.flightline.highline.edu/seismic/SeismicGraph.htm


I grade the submitted pre-lab and lab.

References and Resources

Contact the Author

Please contact the author with questions or suggestions:
Eric M. D. Baer
206-8788-3710 x 3513

Controlled Vocabulary Terms

Subject: Geoscience:Geology:Structural Geology:Geophysics and Structural Geology, Geoscience:Geology, Geology:Geophysics
Resource Type: Computer Applications, Activities:Project, Classroom Activity, Lab Activity
Inquiry Level: Open-Ended Exploration, Guided Inquiry
Special Interest: Quantitative, Geo2YC- OLD DO NOT USE, Hazards, Computer-Based, 2YC:Geo2YC
Grade Level: College Upper (15-16), College Lower (13-14)
Learning Environment: Project-Based, Laboratory
Quantitative Skills: Units and Unit Conversions, Problem Solving:Equations, Problem Solving, Probability and Statistics:Describing Data Distribution, Models and Modeling, Graphs, Geometry and Trigonometry, Arithmetic/Computation
Ready for Use: Ready to Use:Tested, Ready to Use
Use: Enabling Student Investigation:Analyze model behavior, Enabling Student Investigation
Data Source: Synthetic/Model Data
Earth System Topics: Solar System and Astronomy, Solid Earth, Human Dimensions:Natural Hazards
Quantitative Skills Activity Type: Lab Activity, Classroom Activity
Science Background Required: Basic scientific background required, Broadly accessible
Topics: Solid Earth:Structural Geology:Geophysics and Structural Geology/Earthquakes/Seismic Reflection Profiling, Solid Earth

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